The present invention relates to angioplasty and, in particular, to a dilatation balloon catheter.
Angioplasty has gained wide acceptance in recent years as an efficient and effective method for treating types of vascular diseases. In particular, angioplasty is widely used for opening stenoses in the coronary arteries. It is also used for treatment of stenoses in other parts of the vascular system.
A common form of angioplasty makes use of a dilatation catheter which has an inflatable balloon at its distal end. With the aid of fluoroscopy, a physician guides the catheter through the vascular system until the balloon is positioned across the stenosis. The balloon is then inflated by supplying fluid pressure through an inflation lumen to the balloon. Inflation of the balloon causes stretching of the artery and a pressing of the lesion into the artery wall to reestablish acceptable blood flow through the artery.
It is apparent that treatment with a dilatation catheter requires that the catheter reach and cross a stenosis. In order to extend treatment to very tight stenosis with small openings, there has been a continuing effort to reduce the profile (and shaft diameter) of the catheter. In addition, a successful dilatation catheter must be sufficiently flexible to pass through tight curvatures through the very tortuous path of the vascular system.
A further requirement of a successful dilatation catheter is its "pushability." This involves a transmission of longitudinal force along the catheter from its proximal end to its distal end so that a physician can push the catheter through the vascular system and the stenosis.
It is a common practice to employ a guide wire to establish the path to the stenosis. The dilatation catheter is then fed over the guide wire until the balloon is positioned within the stenosis. As an alternative, the catheter can serve as its own guide wire. One disadvantage to the self-guiding approach is that there is nothing to maintain the desired position within the vascular system when replacing the catheter--as when a larger or smaller balloon is desired, for example. Such replacement requires that the path to the stenosis must be reestablished when the catheter is replaced.
The use of a catheter assembly employing a guide wire provides the advantage of maintaining a path to the stenosis during a catheter exchange. One problem with many so-called "over-the-wire" catheters is the need to accommodate the guide wire within the catheter which has often been accomplished through the provision of a separate guide wire lumen. This has resulted in a larger profile (and shaft) to allow for the separate guide wire lumen.